Carburetor



@ct. 31, 19330 A. M. PRENTESS CARBURETOR Filed May 11, 1931 IN VENTOR.41/605 77/\/ M PREN775 A TTORNE Y.

Patented @ct. 31, 1933 PATENT @FF LEDES EW CAREUEETQDHE Augustin M.Prentiss, San Antonio, Tern, assignor to Bendix Stromberg (CarburetorCompany,

South Bend, l[nd., a corporation of llllinois Application May llll,1931.. Serial No. 536,398

7 Claims.

This invention pertains to carburetors and more particularly hasreference to temperature controlled acceleration pumps therefor.

It has long been known in the carburetor art that the amount ofadditional fuel supplied to the mixture for accelerating the enginevaries with the temperature of the engine and liquid fuel (gasoline).Thus, for a cold engine a relatively large accelerating charge of liquidfuel is required, and as the engine warms up, a gradually decreasingamount of accelerating fuel is needed until a certain temperature isreached when no accelerating fuel is necessary, and if any is supplied,it not only does not assist acceleration, but actually retards it.

Another problem of long standing in the carburetor art has been toeliminate flat spots in passing from idle, or slow speed operation, tomain jet, or high speed operation. Flat spots 39 are particularlydifficult to eliminate under quick acceleration for the reason thatheretofore ac-= celerating devices have always injected a supplementarycharge of liquid fuel into the mixing chamber in the region ofrelatively low suction below the throttle, and have never fed additionalfuel into the mixture outlet in the region of high suction above thethrottle during the period of transition from idle to main jetoperation. I

have found that when the throttle is suddenly opened for quick andpowerful acceleration, there is not time enough (with the relativelyweak suction then in the mixing chamber) to transmit sufficientadditional fuel from the mixing chamber to the intake manifold tocompensate for the condensation due to drop in vacuum therein, and

a flat spot results regardless of how vigorous a charge is delivered bythe accelerating pump. The time and space factors are the controllingelements in this problem and I have found that these can only beovercome by delivering a portion of the accelerating charge above thethrottle in the region of high suction. In this way, the time and lengthof travel of a portion of the accelerating charge is considerablyreduced and 5 the consequent fiat spot is eliminated.

Moreover, as stated above, when the temperature of the engine and liquidfuel approaches normal summer operating temperatures, which often exceedthe boiling point of the lightest fraction of the liquid fuel, no extrafuel is needed for ac- (Cll. 261-341) celeration, and hence it isnecessary that'a temperature control be placed upon that portion of theaccelerating charge fed into the mixture out-= let above the throttle,as well as for the remain der of the charge that is fed into the mixingchamber below the throttle.

An object of this invention is to overcome the above difficulties byproviding an acceleration pump that delivers a portion of theaccelerating charge into the mixture outlet in the region of relativelyhigh vacuum above the throttle.

Another object of my invention is to provide a temperature control foran acceleration pump which depends primarily upon the temperature of theliquid fuel rather than upon the temperature of the air or body of thecarburetor.

Still another object of this invention is to pro vide a temperaturecontrol for an acceleration pump that not only regulates the output ofthe pump into the mixing chamber below the throttle, but also regulatesthat portion of the output that is discharged into the mixture outletabove the throttle.

With these and other objects in view, which may be incident to myimprovements, my inven tion consists in the combination and arrangementof elements hereinafter described and illustrated in the accompanyingdrawing in which Figure 1 shows in central longitudinal section acarburetor embodying my improvements; and Figure 2 shows a similar view,on an enlarged scale, of the idle discharge outlet and valve.

Referring to the drawing, the reference numeral 1 denotes the body ofthe carburetor which consists of the usual air intake 2, mixing chamber3, and mixture outlet 4 controlled by a throttle valve 5. Castintegrally with the body 1 is a liquid fuel float chamber 6, which isclosed with a cover 32 and supplied with fuel by a pipe 2' leading to amain supply tank (not shown). Within the chamber 6 is a float 8 whichacts on valve 9 to maintain the level of the liquid fuel in said chamber at the normal static level indicated by the line Positioned withinthe mixing chamber 3 is a main fuel nozzle 10 which communicates withfloat chamber 6, through passageways 11 and 12 which latter iscontrolled by a needle valve 13 serving to regulate the main jetdischarge and thus control the normal operating mixture. The

till

idle or slow speed feed is delivered through a passageway 14; and aplurality of ports 15 and 163 which bestride the throttle when in closedposition, in a well known manner. Adjacent port on the opposite side ofpassageway 14! is an air bleed port 17, controlled by a manuallyadjustable valve 18, which regulates the normal idle feed by admittingatmospheric air to modify the suction in passageway l l.

Cast integrally with the body 1 and positioned within floatchamber 6, isan acceleration pump cylinder 19 which is separated from the floatchamber 6 by a double wall partition 20 through which are twopassageways 21 and 22 leading from cylinder 19 to float chamber 6. Thebottom passageway 22' through which liquid fuel is supplied from floatchamber 6 to cylinder 19 is provided with aball check valve 23 whichprevents the return of fuel from cylinder 19 to chamber d. Up-= perpassageway 21 permits air to pass freely between chamber 6 and cylinder19 so that the air pressures in the upper parts thereof may be equal atall times.

Slidably mounted in cylinder 19 is a stem 2% which passes through guideholes in cover 32 and bottom of cylinder 19 and extends both above andbelow cylinder 19 as shown in the drawing. The top of stem 24 isprovided with a flat head 25 upon which bears a roller 26 carried on thefree end of a lever 27 which is pivotally attached at 28 to the body 1of the carburetor. Throttle 5 is mounted upon a shaft 29 to one end ofwhich is fixedly attached an operating arm 30 and a cam 31 which latterbears against lever 27 and depresses it whenever arm 30 is rotated in adownward direction to open the throttle 5.

Surrounding stem 24.- between head 25 and the cover 32 of float chamber6 is a helical spring 33 which normally tends to keep stem 2%- in its uppermost position as determined by contact of collar 34 (fixed on stem24) with cover 32.

Slidably mounted upon stem 24 and adapted for reciprocation in cylinder19 is a piston 35 which is normally held in contact with a flange 36 onstem 24. by a helical spring 37. The lower part of stem 24 is providedwith a central passageway 39 which extends from the bottom of stem 24.-to a point just above flange 36 and there makes a right angle bend andterminates in a port dill which is adapted to be covered and uncoveredby the movement of piston 35 on stem 2% as will be hereinafter morefully explained.

In axial alignment below cylinder 19 is an aux-- iliary chamber ll intowhich liquid fuel is fed. from cylinder 19 through passageway 39 whenport 40 is uncovered by piston 35. From chamber d1 fuel is dischargedthrough a metering orifice d2 in passageway 11, said orifice forming theseat of a valve 4.3 which is actuated by a semi-circular thermostaticelement id, attached to the wall of chamber 41 by a screw 45 andarranged to move valve 43 against seat l2 with a rise in fuel temperature and to withdraw said valve from his seat with a fall in fueltemperature, thus regulating the flow of accelerating fuel inversely inaccord ance with its temperature. A plug 461 in the bot== tom of chamber4:1 permits draining and clearing said chamber.

The wall oi cylinder 1o, adjacent passage and at a point just below thehighest point of travel of piston 35, is provided with a passageway 47establishing communicating between cylinder 19 and passageway 14: of theidle feed system. Passageway 47 is controlled by a valve 48 held to itsseat by a helical so which surrounds nesaseo a stem to which is attachedto and actuated by a thermostatic element 51 secured to the wall of body1 by screws 52. Spring s9 is of such strengththat it holds ball valve 48on its seat against the maximum suction existing at any time in passage,

way is, but whenever appreciable pressure is exerted on the liquid fuelin cylinder 19 by piston 35, spring 49 is overcome, and valve'dfi openspassageway d7.

Stem 50 is so arranged as to be moved by thermostat 51 toward. ball 48with a rise in temperature and thus restrict the passageway 47 bylimiting the opening movement of theball. The opposite action takesplace with a fall in temperature of the liquid fuel, and thus the flowof ac-= celeratingiuel to the idle portsld and it is regulated inverselyin accordance with said temperat ture.

Passageway 14, below valve 5a is provided with a ball check valve 53 toprevent accelerating fuel discharged through passageway d7 from escapingback through main nozzle 1c. The seat 5% of valve 53 is a calibratedrestriction to meter the flow of liquid fuel when this valve is open.

The operation of my device is as follows: When the. throttle 5 is closedcam 31 just contacts with lever 27 but exerts no pressure thereon. Underthese conditions spring 33 keeps stem 2d in its uppermost position, thatis, with collar as contacting with cover 32, and spring 37 keeps piston35 iri contact with collar 36, thus closing port so. Liquid fuel flowsfrom float chamber 6 through passage 22 into cylinder 19 and thencethrough port so, passage 39, chamber ill, and passage ii to main jet l0and idle feed passageway id where it rises to the line X-X whenever theengine is at rest.

It now the throttle is opened cam 31 bears upon lever 27 which in turndepresses stem 24. The downward thrust of stem 2%, transmitted throughcollar 34'.- and spring 37, to piston 35, causes piston 35 to exert adownward pressure on the column of liquid fuel in cylinder 19 below thepiston. The reaction of the liquid against piston 35 retards itsdownward travel while the downward travel of stem 24.- is not soretarded, with the result that stem 24 travels faster than piston 35,and spring 37 is thereby compressed and port so uncovered. The liquidfuel in cylinder 19, being under in creased pressure from piston 35,escapes rapidly through passageway 39, chamber 41, and pas= sageway 11to main jet 10 where it is discharged as a supplement to the normal howof liquid fuel from chamber 6 through passageway 12 to nozzle id. Aportion of the liquid fuel escaping through passageway 39 also reachespassageway 14 and rises above the line Ill-X. However, due to therelative resistance to flow and the short length of mainnozzle 10, ascompared to passage 14, and to the metering restriction in valve seatas. the rise of liquid fuel in passage 14 is not suiidcient to dischargethrough ports 15 and 16.

When piston 35 first starts on its downward stroke, and before port sois uncovered, a small portion of liquid fuel in cylinder ll-B escapesthrough passageway 4? into passage 14.. Here check valve 53, preventsits esca main nozzle it), so that it rises in passage 14 and dischargesthrough idle ports 15 and it a supplementary iced to the fuel that isnormally fed through these ports by suction when the throttle is in restricted position.

as soon as the lower edge of piston to over passageway at, thissupplementary accelera tion feed through idle ports 15 and it is cutoil,

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nesasea so that it is only for a brief interval of time during the firstpart of the stroke of the acceleration pump that this additionalacceleration feed through the idle system is supplied. But it is just atthis interval that flat spots have occurred in the prior art devicesbecause of the length of time required for the additional acceleratingfuel to reach the intake manifold when fed through the longer and morecircuitous channel through the mixing chamber. This delay of theacceleration fuel in reaching the intake manifold, when the throttle issuddenly opened, is caused by the in= herent inertia of the liquid mass,its friction in passing through various chambers and passageways, andthe fact that it is discharged into the mixing chamber in the region ofrelatively low suction below the throttle from which it still has aconsiderable distance to travel before it reaches the intake manifold.

By my provision of a supplementary passage= way direct from theacceleration pump cylinder through the idle feed system into the mixtureout let above the throttle, I greatly reduce the time required for thefirst portion of the accelerating charge to reach the intake manifoldand thus eliminate the flat spots which have proven so troublesome inthe prior art.

If the throttle 5 is opened slowly, as when rapid acceleration is notdesired, there is sufficient clearance between piston 35 and cylinder 19to permit the liquid fuel in cylinder 19 to escape past piston 35 sothat not enough liquid pressure is developed to compress spring 37 anduncover port l0 or to unseat valve l8. Under these circum-- stances noliquid fuel escapes from cylinder 19 but merely surges from below piston35 to the space above it. Check valve 23 prevents any return of liquidfuel from cylinder 19 to float chamber 6.

The above described operation has been premised upon valves a3 and 48being open to permit how of liquid therethrough, but these valves areonly fully opened by their thermostatic controls at the lowest operatingtemperature of the carburetor when the maximum volume of acceleratingcharge is desired. As the temperature rises, valves 43 and 48 aregradually closed until the highest operating temperature of thecarburetor is reached when they completely cut ofi fuel flow, and noaccelerating charge is supplied when the throttle is suddenly opened, asnone is desired at this temperature. When valves 43 and 48 are closedand the throttle is suddenly opened, stem 24 descends as before, butsince no fuel escapes from cylinder 19, piston 35 is held in itsoriginal position and spring 37 is correspondingly compressed to take upthe travel of stem 24. If now the throttle is held open, piston 35gradually descends as the liquid fuel escapes past it to the space aboveit in cylinder 19. If now the throttle is suddenly closed, the volume ofliquid fuel trapped above piston 35 is returned to float chamber 6 byway of passage 21.

The rate of opening and closing of valves 43 and 48 can be regulated bycalibrating thermostatic elements 414 and 51 so that the amount ofaccelerating charge supplied at any time is in versely proportional tothe temperature of the liquid fuel.

While I have shown and described the preferred embodiment of myinvention, I desire it to be understood that I do not limit myself tothe constructional details disclosed by way of illustra= tion, as it isapparent that these may be changed and modified by those skilled in theart without departing from the spirit of my invention or exceeding thescope of the appended claims.

I claim:

1. In a carburetor having a fuel nozzle and a mixture outlet controlledby a throttle, an acceleration device comprising means to deliver aportion of its accelerating fuel charge direct to the mixture outletabove the throttle and a portion to the fuel nozzle, and separate meansfor regulating each portion of the accelerating charge in accordancewith the temperature of said fuel.

2. A carburetor comprising a main fuel nozzle, an idling fuel nozzle,and an accelerating device adapted to discharge a portion of its fuelcharge through said main nozzle and a portion through said idlingnozzle, and separate means for regulating each portion of theaccelerating charge in accordance with the temperature of said fuel.

3. In a carburetor, a throttle, a mixture outlet above said throttle, amixing chamber below said throttle, and an accelerating devicecomprising means to deliver a portion of its fuel charge to said outletand a portion to said chamber, and separate means for regulating eachportion of the accelerating charge in accordance with the liquid fueltemperature.

a. A carburetor comprising a mixture outlet, a throttle controlling saidoutlet, a float chamber,

an idling jet leading from said chamber and discharging above thethrottle, and an accelerating pump positioned within said chamber,comprising means to deliver a portion of its fuel charge direct to saididling jet, and means to regulate said portion of the accelerating fuelcharge in accordance with the temperature of said fuel] 5. A carburetorcomprising a mixture outlet, a throttle controlling said outlet, a floatchamber, an idling jet leading from said chamber and discharging abovethe throttle, and an accelerating pump comprising means to deliver aportion of its fuel charge direct to said idling jet, and means toregulate said portion of the accelerating fuel charge in accordance withthe temperature of said fuel.

6. In a carburetor, a throttle, a mixture outlet above said throttle,'amixing chamber below said throttle, and an accelerating devicecomprising means to successively deliver a portion of its output to saidoutlet and a portion of said chamber, and separate means to regulate theamount of each portion in accordance withthe liquid fuel temperature.

"I. A carburetor comprising a main fuel nozzle,

an idle fuel feed passageway, an accelerating device adapted tosuccessively discharge a portion of its fuel charge through said nozzleand a portion through said passageway, and separate thermal-responsivemeans for regulating the amount of each portion of the acceleratingcharge in accordance with the temperature of the liquid fuel.

AUGUSTIN M. PRENTISS.

